The present invention relates generally to a crop-drying system, and more specifically to a crop-drying system which employs a solar pre-heat chamber which delivers solar pre-heated air either directly to the crop-drying bin, or which may be mixed with air heated additionally by conventional burners. The system has been found to be valuable in conserving energy which would otherwise be necessary for heating the air, such as energy derived through the burning of conventional fuels such as liquified petroleum gas or the like. A conventional fan is normally employed to drive the air through the system, and means are provided to provide input air to the fan in the event the inlet port to the fan chamber becomes clogged with debris or film from the solar pre-heat chamber.
In drying of cash crops, such as corn, wheat, soybeans and the like, a grain-confining bin is employed having generally imperforate walls and top, with an air discharge vent being employed at the top of the bin. A perforated false bottom is employed in the bin so as to permit the admission and transfer of heated air through the false bottom, through the grain, and thence outwardly through the upper vent. An impeller is provided for forcing drying air through the system including the zone beneath the false bottom, the grain charge, and thence out through the vent.
In most conventional systems, a liquified petroleum gas burner is employed which heats the air being admitted to the drying bin. This heater preferably has a sensor activated burner, with the sensor detecting the relative humidity of the air being admitted to the grain-confining bin. For most drying purposes, air having a relative humidity of less than 50% must be employed, in order to achieve effective drying of the grain within the bin. For partially dried grain, the relative humidity requirements of the incoming air may, in certain instances, be less than 50%. It has been found that normal ambient air, when heated in a solar pre-heat chamber can be effectively elevated in temperature for temperature rises of up to 30.degree. F. and more, and thus for most normal autumn days, when drying is being undertaken, the solar pre-heat chamber may be utilized effectively without requiring supplemental heat from the liquified petroluem gas burner. Obviously, these conditions apply only during the sunlight hours, and night-time hours may require more frequent use and cycling of the liquified petroleum gas burner.